A major goal of modern neuroscience is the complete understanding of neuronal circuits development and function in an intact behaving animal.

Figure 1 : Dorsal view of GFP specific expression in the tectum of a 7dpf larva in agene trap line. White dashed line marks the boundary between the Neuropil region and the cellular layer where tectal periventricular neurons cell bodies are located (intense green region).

Our group examines neural circuit formation and function in the visual system using in vivo time-lapse microscopy and novel “optogenetic” approaches to monitor and perturb neuronal activity. The zebrafish preparation is ideal for the in vivo study of the visual system (retina and optic tectum) development and function. First of all, the zebrafish brain is much smaller (< 1mm) than that of mammals, while being equally well differentiated (Fig.1). Importantly, the larval fish brain is transparent. This feature enables optical approaches, such as using genetically encoded fluorescent reporters of axonal transport and synaptic formation.

We are currently working on two main research projects:

1. We are investigating the axonal trafficking in vivo in the retinotectal neurons (Fig.2). The correct trafficking of macromolecular complexes and organelles along the axon is crucial to regulate several aspects of neuronal function, including neuronal survival, axon branch extension, and synaptogenesis. Kinesin superfamily proteins (KIFs) and cytoplasmic dynein/dynactin complex are the microtubule-associated molecular motors that drive axonal transport. This analysis is carried out using wild type and mutant fish lines using an in vivo confocal microscopy to follow the transport of fluorescently tagged proteins and organelles. The relevance of this project extends to the understanding of several forms of neuronal degeneration diseases in humans (such as amyotrophic lateral sclerosis, ALS) where mutations in molecular motors have been implicated.

2. A second line of research investigated the formation of neuronal circuits within the tectum itself. We are in particular focusing on a particular class of inhibitory interneurons located in the tectum neuropil. We have discovered that their function is crucial for visual size selectivity and tectal response to small and localized stimuli. We are now investigating how the connectivity of these neurons with the retina ganglion cells develops and functions. Again we use confocal time-lapse analysis to follow synaptogenesis in vivo, optogenetics and synaptic tracing to reveal the underling neural circuit.

991 Silve Jet Beluga Rise Ht Hansen Helly Boots Ullr Multicolour Hiking High Monashee Women’s Black W Our final goal is to expand our knowledge of neural circuit development at a cellular and molecular level, to extract general principles that can be relevant to the study and understanding human neurological disorders.